Acceleration apparatus for the production of x-rays and neutrons



United States Patent US. Cl. 25084.5 19 Claims ABSTRACT OF THE DISCLOSURE Acceleration apparatus having a beam tube with an aluminum target at one end of the tube and a beryllium target at the other end of the tube, the targets being respectively provided with a positive accelerating potential and a negative accelerating potential. A particle source, utilizing an ionization mechanism and a propelling magnetic field, is employed to feed electrons and positively charged particles into the beam tube at a place intermediate the targets. A third target, uranium, is disposed externally of the beam tube in the vicinity of the beryllium target. The electrons, as they are fed into the beam tube are accelerated toward and bombard the aluminum target to produce X-rays. The positively charged particles, as they are fed into the beam tube, are accelerated toward and bombard the beryllium target. It is known, that when beryllium is bombarded by positively charged particles, the reaction releases neutrons. The released neutrons in turn bombard the uranium. The latter reaction produces plutonium 239. The electrons and the positively charged particles (propellant masses) are accelerated in substantially a vacuum environment. The high voltage source for energizing the aluminum target and the beryllium target features a first hollow substantially spherical ball, such as that used in a Van de Graff generator. A second hollow substantially spherical ball is disposed adjacent, and electrically connected, to the Van de Graft ball. Preferably the two balls are covered with an insulating plastic shield to decrease corona discharge.

Another object is to provide an inexpensive accelerator.

Another object is the provision of a particle source, utilizing an ionization mechanism and a propelling magnetic field, to feed electrons and positively charged particles into a beam tube.

Another object of my invention is to employ helium gas, in which an atom is made up of two protons, two neutrons, and two electrons.

Another object is to obtain a high voltage source from a Van de Graif hollow ball generator, with the addition of a secondary hollow ball disposed adjacent, and electrically connected, to the Van de Graif ball, both balls being covered by a plastic insulating shield to decrease corona discharge.

Another object is to utilize a magnetic field to propel positively charged particles (propellant masses) into an electro-static field, where the masses are then accelerated by the electro-static field.

Another object is to utilize a magnetic field to propel electrons into an electro-static field, where the electrons are then accelerated by the electro-static field.

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Another object is to provide a propulsion system utilizing a magnetic field in combination with an electrostatic field.

Other objects and a fuller understanding of this ininvention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view, partly diagrammatic, of an acceleration apparatus embodying the features of my invention, the long vertical tube being the acceleration tube, the short tube, disposed in a plane perpendicular to the acceleration tube, being the ionization tube, and the interconnecting tube, disposed in a plane vertical with the acceleration tube, being the feed tube which feed electrons and positively charged particles to the acceleration tube.

FIG. 2 is a cross-sectional view taken horizontally through the acceleration tube, the interconnecting feed tube and the ionization tube, showing the electrodes for ionizing the gas in the ionization tube;

FIG. 3 is a cross-sectional view, taken along the line 3-3 of FIG. 2, showing principally an arcuately contoured external conductor disposed adjacent the ionization tube to produce a magnetic field for propelling electrons and positively charged particles into the feed tube and thence into the acceleration tube;

FIG. 4 is an enlarged view of the Van de Graft ball, together with the additional (secondary) ball shown in section, into which the upper end of the acceleration tube projects, the view also showing both balls being covered by a plastic insulating shield; and,

FIG. 5 is an enlarged cross-sectional view of the lower end of the acceleration tube, showing the beryllium target (pellets) inside the tube and the uranium target outside the tube in a suitable sealed crucible.

With reference to the drawings, my acceleration apparatus comprises, generally, a Van de Graif ball generator 10, an additional (secondary) ball 11 disposed adjacent, and electrically connected, to the Van de Graif ball 10, a vertical acceleration tube 12, an ionization tube 13, and an interconnecting feed tube 14.

For simplicity in making the drawings, the Van de Graff ball 10 and the additional, or secondary, ball 11 are shown as being spheres, but it is understood that these balls in practice are not exactly true spheres, but are modified spheres. The balls 10 and 11 are hollow, and, in the embodiment of my invention, are approximately 10 inches in diameter, but the size may be varied. I find that a higher voltage may be achieved by covering the balls 10 and 11 with a plastic insulating material or shield 22, such as polyethylene. This shield reduced the corona discharge and increased the voltage from approximately 0.5 million volts to approximately 1.0 million volts. The secondary ball 11 is provided with an aperture 17. The upper end of the acceleration tube, designated by the reference character 18, is disposed to project through the aperture 17 into the inside of the secondary ball 11, see FIG. 4. As shown, the upper end 18 of the acceleration tube 12 is covered by a plate 19, which is preferably aluminum. The plate 19 may be sealed to the upper end 18 by any suitable sealing material, such as by an epoxy 20. The seal produced thereby is vacuum tight. Extending upwardly from the aluminum plate 19, is a wire 21 which electrical contacts the inside of the hollow secondary ball 11. Thus, the aluminum plate 19 is provided with a high positive accelerating potential. The aluminum plate 19 has an internal surface exposed to the inside of the acceleration tube 12. This exposed internal surface constitutes a first target to be bombarded by the electrons to produce X-rays.

A second target, disposed to be bombarded by positively charged particles, is located in the bottom end of the acceleration tube, designated by the reference character 25. The second target comprises beryllium pellets 26. The first and second targets 19 and 26 are respectively provided with a positive and a negative accelerating potential. An electro-static field is thus established between the two targets. The bottom end 25 of the acceleration tube 12 is closed off by a zinc plate 27. The zinc plate may be sealed to the lower end 25 by any suitable sealing material such as by an epoxy 28. The seal produced thereby is vacuum tight.

A third target is located externally of the lower end 25 of the acceleration tube 12, directly below the second target. The third target comprises uranium, designated by the reference character 29, is disposed in a crucible 30 having its upper edge sealed to the bottom surface of the zinc plate 27. The lower end 25 of the acceleration tube 12 may be protected from radiation by any suitable means, such as being immersed in a water container 31.

The ionization tube 13 has first and second end tubular portions 34 and 35 and an intermediate tubular portion 36 therebetween. The right-hand end of the feed tube 14 is connected to and is in communication with the intermediate tubular portion 36. The left-hand end of the feed tube 14 is connected to and is in communication With the acceleration tube 12. The ionization tube 13, as well as the acceleration tube 12 and the feed tube 14 are preferably made of glass. A gaseous source, identified by the reference character 37 is connected to the first end 34 of the ionization tube 13. The flow of gas to the ionization tube 13 may be controlled by a valve 38. A vacuum pump, identified by the reference character 39 is connected to the second end 35 of the ionization tube 13. The entire tubular system, including the acceleration tube 12, the ionization tube 13 and the feed tube 14 constitutes a sealed evacuated envelope.

A first electrode 41 is disposed within the first end tubular portion 34 of the ionization tube 13 and a second electrode 42 is disposed within the second end tubular portion 35. The electrodes 41 and 42 are adapted to be energized by a suitable potential source indicated by the reference character 43. The electrode 41 may be connected to the potential source 43 by a conductor 45 and the electrode 42 may be connected to the potential source 43 by a conductor 46 and by an arcuately shaped conductor 47 disposed externally of the intermediate tubular 36, substantially opposite the location where the righthand end of the feed tube 14 is connected to the ionization tube 13. The conductors direct current to flow through the arcuately shaped conductor in a direction to establish a field for repelling electrons or positively charged particles (masses), as the case may be, into the feed tube 14 and thence into the acceleration tube 12. In the case when the electrons are repelled, the current flows through the arcuately shaped conductor 47 in a direction as to establish a field which may be characterized as being negatively polarized, and in the case when the positively charged particles are repelled, the current flows through the arcuately shaped conductor in a reverse direction as to establish a field which may be characterized as being positively polarized. Thus, the potential source 43 may comprise any suitable device providing a potential in the neighborhood of about 10,000 volts sufiicient to ionize the gas.

The gaseous source 37 preferably comprises helium, of which an atom is made up of two protons, t-wo neutrons and two electrons. Other gases may be used instead of helium, but I find helium is very satisfactory. The ionization tube and the propelling magnetic field may be characterized as particle source means for feeding electrons or positively charge particles to the acceleration tube 12. When the magnetic field is said to be positively polarized, the electrons of the ionized gas are attracted toward the arcuately shaped conductor 47. Under this condition at least one electron is considered to be removed from the helium atom, leaving a nucleus comprising two protons and two neutrons with 'one remaining electron, thereby producing a helium ion which is posi tively charged. The positively polarized field acts to repel the helium ion into the feed tube 14 and thence into the acceleration tube 12. The nucleus and the one remaining electron upon entering the acceleration tube 12 comes under the influence of the accelerating potential on the aluminum plate 19. Here, the one remaining electron is attracted by the positive charge on the aluminum plate and the nucleus is repelled toward the beryllium. As a consequence, the electrons bombard the aluminum plate and produce X-rays, and the nucleus bombard the beryllium. The X-rays produced by my acceleration apparatus because of their high energy, may be referred to as gamma rays. The apparatus is inexpensive and makes a good source for industrial X-raying. My device produced substantially one mev. gamma rays. The nucleus, having the positive charge, is repelled toward and bombards the beryllium in the bottom of the acceleration tube 12. It is known that, when beryllium is bombarded by positively charged particles, the reaction releases neutrons. These released neutrons, in turn, bombard the uranium in the crucible 30. This latter reaction in my device produced plutonium 239. In my invention, the electrons and the positively charged particles (propellant masses) are accelerated in substantially a vacuum environment. It is seen that an aspect of my invention is to utilize a magnetic field to propel the electrons and the positively charged particles (propellant masses) into an electrostatic field, where they are then accelerated by the electro static field.

In an acceleration device embodying my invention, the acceleration tube 12, the ionization tube 13 and the feed tube 14 may have a diameter in the range of approximately to 1 inch. The acceleration tube 12 may have a length of about five feet. The feed tube 14 may be connected to the acceleration tube 12 at a place approximately one foot from the upper end portion 18. The ionization tube 13 may have a length of about five inches with the distance between the electrodes 41 and 42 of about 2 /2 to 3 inches. The feed tube 14 may have a length of about 2 to 3 inches. These dimensions may, however, be varied.

There are several possible uses of this device. It can be used as a source of high energy X-rays for industrial X-raying and for medical X-rays, the advantages being; higher energies and densities available making exposure times shorter and ease of X-raying thick, dense materials easier. A source of neutrons, alpha (positively charged) particles, protons, gamma rays, and electrons is another function. The neutrons can be used for preparation of tracer quantities of radioisotopes for laboratory use in high schools and for tracers for medical research and treatment. It can inject the above particles into larger particle accelerators. It is itself an accelerator suitable for research into low energy nuclear physics. It can be used for X-ray diffraction analysis, neutron activation analysis, and gamma ray spectroscopy. My invention also finds utility where a magnetic field is used to propel electron and positively charged particles (propellant masses) into an electro-static field, where they are then accelerated by the electro-static field.

Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

What is claimed is:

1. Acceleration apparatus comprising an acceleration tube having first and second end tube portions and an intermediate tube portion therebetween, a feed tube having first and second tube ends with said first tube end connected to and communicating with said intermediate tube portion, said acceleration tube and said feed tube constituting a sealed envelope and including electrical insulating material, means for reducing the pressure in said sealed envelope, first target means disposed at said first end tube portion, second target means disposed at said second end tube portion, high voltage source means for providing a positive accelerating potential on said first target means and a negative accelerating potential on said second target means, particle source means connected to said second tube end of said feed tube for introducing electrons and positively charged particles into said intermediate tube portion through said feed tube, said accelerating potential on said first target means accelerating said electrons from said feed tube through said acceleration tube toward said first target means and thereby causing said electrons to bombard said first target means to release X-rays, said accelerating potential on said second target means accelerating'said positively charged particles from said feed tube through said acceleration tube toward said second target means and thereby causing said positively charged particles to bombard said second target means to release neutrons.

2. Acceleration apparatus comprising an acceleration tube having first and second end tube portions and an intermediate tube portion therebetween, a feed tube having first and second tube ends with said first tube end connected to and communicating with said intermediate tube portion, said acceleration tube and said feed tube constituting a sealed envelope and including electrical insulating material, means for reducing the pressure in said sealed envelope, first target means disposed at said first end tube portion, second target means disposed at said second end tube portion, high voltage source means for providing a positive accelerating potential on said first target means and a negative accelerating potential on said second target means, means connected to said second tube end of said feed tube for introducing electrons into said intermediate tube portion through said feed tube, said accelerating potential on said first target means accelerating said electrons from said feed tube through said acceleration tube toward said first target means and thereby causing said electrons to bombard said first target means to release X-rays.

3. Acceleration apparatus comprising an acceleration tube having first and second end tube portions and an intermediate tube portion therebetween, a feed tube having first and second tube ends with said first tube end connected to and communicating with said intermediate tube portion, said acceleration tube and said feed tube constituting a sealed envelope and including electrical insulating material, means for reducing the pressure in said sealed envelope, first target means disposed at said first end tube portion, second target means disposed at said second end tube portion, high voltage source means for providing a positive accelerating potential on said first target means and a negative accelerating potential on said second target means, means connected to said second tube end of said feed tube for introducing positively charged particles into said intermediate tube portion through said feed tube, said accelerating potential on said second target means accelerating said positively charged particles from said feed tube through said acceleration tube toward said second target means and thereby causing said positively charged particles to bom-- bard said second target means to release neutrons.

4. The structure of claim 1, wherein said first target means comprises a metallic member having surface means exposed to the reduced pressure in said sealed envelope.

5. The structure of claim 1, wherein said second target means comprises metallic material disposed internally of the second end tube portion and having surface means exposed to the reduced pressure in said sealed envelope, said metallic material upon bombardment by said positively charged particles releasing neutrons.

6. The structure of claim 1, wherein said second target comprises beryllium which upon bombardment by said positively charged particles releases neutrons.

7. The structure of claim 5 having third target means positioned externally of the second end tube portion and disposed to be bombarded by said neutrons.

8. The structure of claim 7, wherein said third target means comprises uranium.

9. The structure of claim 1, wherein said particle source means comprises an ionization tubular member having first and second end tubular portions and an intermediate tubular portion therebetween, a feed tubular member having first and second ends with said first end connected to and communicating with said intermediate tubular portion, said second end of said feed tubular member being connected to and in communication with said second tube end of said feed tube, said ionization tubular member and said feed tubular member including electrical insulating material, gaseous source means connected to said first end tubular portion to provide gaseous substance therein, vacuum source means connected to said second end tubular portion, first electrode means disposed within said first end tubular portion of said ionization tubular member, second electrode means disposed within said second end tubular portion of said ionization tubular member, potential source means for energizing said first and second electrodes to ionize said gaseous substance, electrical connection means for connecting said first and second electrode means to said potential source means, said connection means including external conduc tor means disposed externally of said intermediate tubular portion of said ionization tubular member and disposed on a side of said intermediate tubular portion substantially opposite the location where said first end of said feed tubular member is connected to said intermediate tubular portion, said connection means directing current to fiow through said external conductor means in a direction to establish a field for directing electrons into said acceleration tube.

10. The structure of claim 1, wherein said particles source means comprises an ionization tubular member having first and second end tubular portions and an intermediate tubular portion thereebtween, a feed tubular member having first and second ends With said first end connected to and communicating with said intermediate tubular portion, said second end of said feed tubular member being connected to and in communication with said second tube end of said feed tube, said ionization tubular member and said feed tubular member including electrical insulating material, gaseous source means connected to said first end tubular portion to provide a. gaseous substance therein, vacuum source means connected to said second end tubular portion, first electrode means disposed within said first end tubular portion of said ionization tubular member, second electrode means disposed within said second end tubular portion of said ionization tubular member, potental source means for energizing said first and second electrodes to ionize said gaseous substance, electrical connection means for connecting said first and second electrode means to said potential source means, said connection means including external conductor means disposed externally of said intermediate tubular portion of said ionization tubular mem her and disposed on a side of said intermediate tubular portion substantially opposite the location where said first end of said feed tubular member is connected to said intermediate tubular portion, said connection means directing current to flow through said external conductor means in a direction to establish a field for directing positively charged particles into said acceleraton tube.

11. The structure of claim 1, wherein said high voltage source means includes a first hollow substantially spherical means, means for energizing said first hollow substantially spherical means to a high positive potential, a second hollow substantially spherical means electrically 7 energized from said first hollow substantially spherical means, said second hollow substantially spherical means having an aperture through which said first end tube portion and said first target means project into the interior of said second hollow substantially spherical means.

12. The structure of claim 11, having electrical insulating material disposed externally of said first and second hollow substantially spherical means to reduce corona discharge so a higher potential is achievable.

13. Particle source means comprising, an ionization tubular member having first and second end tubular portions and an intermeidate tubular portion therebetween, a feed tubular member having a connection end and an exhaust end with said connection end connected to and communicating with said intermediate tubular portion, said exhaust end being connected to a sealed envelope, said ionization tubular member and said feed tubular member including electrical insulating material, gaseous source means connected to said first end tubular portion to provide a gaseous substance in said ionization tubular member, vacuum source means connected to said second end tubular portion, first electrode means disposed Within said first end tubular portion of said ionization tubular member, second electrode means disposed within said second end tubular portion of said ionization tubular member, potential source means for energizing said first and second electrodes to ionize said gaseous substance, electrical connection means for connecting said first and second electrode means to said potential source means, said connection means including external conductor means disposed externally of said intermediate tubular portion of said ionization tubular member and disposed on a side of said intermediate tubular portion substantially opposite the location Where said first end of said feed tubular member is connected to said intermediate tubular portion, said connection means directing current to flow through said external conductor means in a direction to establish a field for propelling positively charged particles from said ionization tubular member into said feed tubular member and out through said exhaust end into said sealed envelope.

14. Particle source means comprising, an ionization tubular member having first and second end tubular portions and an intermediate tubular portion therebetween, a side tubular member having a connection end and an exhaust end with said connection end connected to and communicating with said intermediate tubular portion, said exhaust end being connected to a sealed envelope, said ionization tubular member and said side tubular member including electrical insulating material, gaseous source means connected to said first end tubular portion to provide a gaseous substance in said ionization tubular member, vacuum source means connected to said second end tubular portion, first electrode means disposed within said first end tubular portion of said ionization tubular member, second electrode means disposed within said second end tubular portionof said ionization tubular member, potential source means for energizing said first and second electrodes to ionize said gaseous substance, electrical connection means for connecting said first and second electrode means to-said potential source means, said connection means including external conductor means disposed externally of said intermediate tubular portion of said ionization tubular member and disposed On a side of said intermediate tubular portion substantially opposite the location where said-first end of said side tubular member is connected to said intermediate tubular portion, said connection means directing current to flow through said external conductor means in a direct-ion to establish a field for propelling electrons from said ionization'tubula'i member into said'side tubular member and out through said exhaust end into said sealed envelope.

15. A high voltage source'compiling system compris ing at least one hollow "substantially sphericalconductor surrounded by an insulatingshield, means for electrically energizing said at least one hollow substantiallyspherical conductor from'a high voltage source, and-means for electrically connecting said at'leastonehollow substantially spherical conductor to equipment utilizing high voltage evacuated tubecomprising first and second spaced metallic means therein, means for energizing said first'and second spaced metallic means to provide a posi tive and a negative accelerating" potential respectively thereon, an ionizable gas in said evacuated tube, and first and second spaced electrodesdisposed intermediate said first and second spaced" metallic means and within said evacuated tube for ionizing said gas. 17. An evacuated tub'e"comprising first and second spaced metallic means therein, means for energizing said first'and second spaced metallic means to providea posi tive and a negative accelerating potential respectively thereon, and meansi'ncludihg tubular means forfeeding electrons into said evacuated tub'eat'a place intermediate said spaced metallic means." f

18. An evacuated tube comprising first and' secojnd spaced metallic means therein, 'mean's forenergi-zing said firstandsecond spacedinetallicmeans to provide a positive and a negative' accelerating *potential respectively thereon, andmeans including tubular meansfor" feeding positively charged particles into said evacuated tube at a place intermediate said spaced metallic means.

19. A propulsion system adapted for operation in substantially a vacuum environment, said system having in said substantially vacuum environment first and second spaced metallic means, high voltage means for respectively energizing said first and second spaced metallic means with a positive and a negative accelerating potential to establish an electro-static field, means including a magnetic field for introducing positively charged propellant masses into said electro-static field at a placeintermediate said spaced metallic means, thereby causing acceleration of said propellantmasses in said electro-stataic field in a direction toward said second" spaced metallic means. a

References Cited v UNITED'STATES PATENTS ARCHIE R, BORCHELT, Primary Examiner D. L. WILLIS, Assistant Examiner U.S. Cl.X-.R. 25 0434; 313- 61 

